Annular array transducer

Abstract

A transducer for use in a localization and therapeutic ultrasound system. The transducer of the present invention includes multiple elements that are driven separately. The elements operate together to focus a continuous wave ultrasound beam at a focal zone that is at a variable distance from the elements. The transducer includes a mechanism to adjust the focal distance so that the focal zone may be moved to multiple depths.

We claim: 
     
       1. An ultrasound transducer for use in a visualization and therapy system comprising: a first curved element operable in a plurality of modes, wherein the first curved element provides for imaging in one of the plurality of modes and provides therapy in a second of the plurality of modes;   a second curved element coupled to the first curved element and operable in the second of the plurality of modes, wherein the first curved element and the second curved element operate in combination to provide therapy when in the second of the plurality of modes.   
     
     
       2. The transducer defined in claim 1 wherein the second curved element surrounds the first curved element, such that the first curved element is a central element of the transducer. 
     
     
       3. The transducer defined in claim 1 wherein the second curved element is off in said one of the plurality of modes. 
     
     
       4. A transducer assembly comprising: a plurality of curved elements, wherein each of the plurality of curved elements is driven separately by one of a plurality of signals to generate energy waves as a continuous wave focused at a focal zone a focal distance from the plurality of curved elements, such that an acoustic beam is created by the plurality of curved elements; and   means coupled to the plurality of curved elements for adjusting the focal distance to move the focal zone to one of a plurality of depths while maintaining a same amount of acoustic energy at different depths.   
     
     
       5. The transducer assembly defined in claim 4 wherein each of the plurality of curved elements comprises a concentric circular element, such that the plurality of curved elements form an annular array. 
     
     
       6. The transducer assembly defined in claim 4 wherein each of the plurality of curved elements have substantially the same surface area. 
     
     
       7. The transducer assembly defined in claim 6 wherein each of the plurality of curved elements has a radius selected to maintain a fixed phase separation. 
     
     
       8. The transducer assembly defined in claim 7 wherein the phase separation comprises a π/4 phase separation. 
     
     
       9. The transducer assembly defined in claim 6 wherein one of the plurality of curved elements is centrally located among the plurality of concentric circular annuli, and further wherein said one of the plurality of curved elements is designed for imaging. 
     
     
       10. The transducer assembly defined in claim 4 wherein the focal distance is adjusted by adjusting the phase of the plurality of signals imparted to each of the plurality of curved elements. 
     
     
       11. The transducer assembly defined in claim 10 wherein the means for adjusting includes means for varying the phase of each of the plurality of signals in the range of ±π/4. 
     
     
       12. The transducer assembly defined in claim 4 wherein the means for adjusting comprises drive electronics. 
     
     
       13. A transducer assembly comprising: a plurality of concentric circular curved annuli coupled as an annular array, wherein each of the plurality of concentric circular curved annuli is driven separately by one of a plurality of signals to generate ultrasound waves as a continuous wave focused at a focal point a focal distance from the plurality of concentric circular curved annuli; and   a drive mechanism coupled to the plurality of concentric circular curved annuli, wherein the drive mechanism adjusts the focal distance to one of a plurality of depths by adjusting the phase of the plurality of signals while maintaining a same amount of acoustic energy at different depths.   
     
     
       14. The transducer assembly defined in claim 13 wherein each of the plurality of concentric circular annuli have substantially the same surface area. 
     
     
       15. The transducer assembly defined in claim 13 wherein each of the plurality of concentric curved circular annuli has a radii selected to maintain a fixed phase separation. 
     
     
       16. The transducer assembly defined in claim 15 wherein the phase separation comprises a π/4 phase separation. 
     
     
       17. The transducer assembly defined in claim 13 wherein one of the plurality of concentric circular curved annuli is centrally located and is designed for imaging. 
     
     
       18. The transducer assembly defined in claim 13 wherein the drive mechanism varies the phase of each of the plurality of signals in the range of ±π/4.